[0001] The invention described herein relates generally to a communication device and method
for conserving power for a wireless device through a power save mode while maintaining
more than one aspect of a network connection for the device. In particular, the power
save mode may selectively activate the device to periodically receive and respond
to certain data link signals, such as beacon signals, from a wireless network and
to periodically receive and respond to protocol requests relating to a connection
protocol, such as Internet Protocol (IP), that is used to transmit its traffic over
the network.
[0002] Wireless handheld mobile communication devices perform a variety of functions to
enable mobile users to stay organized and in contact with others in a communication
network through e-mail, schedulers and address books.
[0003] As wireless devices are portable, they connect and communicate with several different
wireless communication networks as they roam. As a wireless device roams, it periodically
scans to determine if it is in communication range of one of the target networks.
Such scans expend power on the device, thereby depleting its battery. Current wireless
devices can be placed in a power saving mode where communications to the connected
wireless network are minimized.
[0004] Typical communications between a device and a network are managed through a set of
layered communication protocols for network communications, such as the Open Systems
Interconnection (OSI)-connection layers. For a network connection following such layered
protocols, different layers may impose different communication signalling requirements
on the device. Each requirement for each layer may need to be adhered to by the device
if the overall network connection is to be maintained. Prior art power save modes
focus strictly on maintaining one layer of a protocol of a network connection, such
as the data link connection, thereby leaving open the possibility of ignoring the
requirements of other layers and losing the connection.
[0005] WO 2004/021592 A1 discloses a power conserving method for a communication device in which, each time
the communication device transmits a signal the device remains active and able to
receive signals for a set period of time before the device is deactivated. The device
is then periodically reactivated at listening intervals to receive beacon signals.
[0006] US 2005/0254444 A1 discloses power conserving method for a communication device in which each a communication
device is deactivated and then periodically reactivated at intervals to receive beacon
signals. The beacon signals include bits identifying devices which have pending messages
which it has not yet received. The devices which have pending messages remain active
to receive them while the devices which do not have pending messages are immediately
deactivated.
[0007] There is a need for a communication device and method which addresses deficiencies
in the prior art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Embodiments of the invention will now be described, by way of example only, with
reference to the accompanying drawings, in which:
- Fig. 1
- is a schematic diagram of a communication network having a plurality of wireless networks
therein that can communicate with a wireless electronic communication device having
a power save mode as provided in an embodiment;
- Fig. 2A
- is a flowchart of exemplary steps executed by the device of Fig. 1 in determining
timing parameters for a power save mode according to an embodiment;
- Fig. 2B
- is a timeline of activation and deactivation periods for the device of Fig. 1 when
operating in a power save mode according to an embodiment;
- Fig. 3
- is a schematic representation of the device of Fig. 1 having a power save mode in
accordance with an embodiment; and
- Fig. 4
- is a block diagram of certain internal components of the device of Fig. 3.
GENERAL
[0009] The description which follows and the embodiments described therein are provided
by way of illustration of an example or examples of particular embodiments of the
principles of the present disclosure. These examples are provided for the purposes
of explanation and not limitation of those principles and of the invention. In the
description which follows, like parts are marked throughout the specification and
the drawings with the same respective reference numerals.
[0010] In a first aspect, a method for maintaining a network layer connection to a network
by a communication device through a transceiver is provided. The method comprises:
in a first cycle, at a first instance in a first period of time monitoring for a Medium
Access Control 'MAC' beacon signal relating to the data link layer connection from
the transceiver during the first period, the first period timed to allow the device
to receive the MAC beacon signal and the first cycle having a frequency based on a
frequency of occurrence of the MAC beacon signal; and in a second cycle, for a second
period beginning at a second instance in the second cycle, monitoring for an Address
Resolution Protocol 'ARP' request for an Internet Protocol 'IP' address relating to
the network layer communication from the transceiver during the second period, the
second cycle having a frequency which is shorter than the frequency of transmission
of the ARP from a host in the network.
[0011] The method may further comprise: in the first cycle, at the first instance re-activating
a communication subsystem in the device and de-activating the communication subsystem
after the end of the first period.
[0012] The method may further comprise: in the second cycle at the second instance re-activating
the communication subsystem and de-activating the communication subsystem after the
end of the second period.
[0013] In the method, the network may be a 802.11-class network.
[0014] In the method, for the first period if the MAC beacon signal indicates broadcast
or multicast traffic from the network intended for the device follows the MAC beacon
signal, the communication subsystem may be de-activated after an end of transmission
of the broadcast or multicast traffic; and if the MAC beacon signal indicates that
no broadcast or multicast traffic from the network intended for the device follows
the beacon signal, the communication subsystem may be de-activated after completion
of reception of the MAC beacon signal.
[0015] In the method, during the second period a unicast frame may be transmitted to a host
in the network by the device.
[0016] In the method, the first cycle may be determined from a delivery traffic indication
map 'DTIM' value in the MAC beacon, such that if the DTIM value equals 1, then the
first cycle may be set to be related to a larger DTIM value.
[0017] In the method, the DTIM value may be used to indicate a de-activation period for
the at least one communication subsystem.
[0018] In the method, a clock in the device may track an elapsed time between receipt of
the ARP request and receipt of a next ARP request to determine the second period of
the power save mode.
[0019] In the method, if the DTIM value equals 1, then the first cycle may be set to span
three MAC beacon signal intervals.
[0020] In the method, the first period may be extended for a predetermined period when broadcast
traffic to the device from the network is being sent to the device to allow the device
to receive the broadcast traffic.
[0021] In the method, the first period may be reduced by a first offset relating to a reactivation
time required by the device to re-activate the at communication subsystem.
[0022] In a second aspect, a communication device having a power save mode is provided.
The device comprises: at least one communication subsystem providing transmission
and reception of signals with a communication network; a microprocessor; a timer;
a first module to selectively activate and de-activate the communication subsystem
when the device is operating in the power save mode; and a second module to control
the first module and the communication subsystem while the device is in the power
save mode such that the communication device is caused to perform selected the steps
of the method as noted in the first aspect.
[0023] In a third aspect, a computer readable medium storing computer readable instructions
executable by a processor of a computing device is provided to cause the device to
implement the any of the steps of the method of the first aspect.
[0024] In other aspects, various combinations of sets and subsets of the above aspects are
provided.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0025] Exemplary details of embodiments are provided herein. Briefly an embodiment provides
a method and system to selectively provide low power mode for a communication device.
When the low power mode is activated, a power save mode for the device is asserted,
where certain components are temporarily de-activated, such as components and modules
relating to communication subsystems for the device. Parameters that determine the
length and frequency of the power save mode are determined from connection requirements
for the device. The connection requirements can relate to requirements for different
layers of an underlying connection model for the network and its traffic.
[0026] First, a description is provided on general concepts and features of a network that
communicates with a device according to an embodiment, including related network connection
requirements for the device. Next, further detail is provided on a power save mode
according to an embodiment and its algorithms that accommodate the connection requirements
for the device. Then, further detail is provided on an exemplary wireless device related
to an embodiment.
[0027] Referring to Fig, 1, details on an exemplary network and communication device having
a power save mode according to an embodiment are provided. Fig. 1 shows communication
system 100 where network 102 provides a suite of applications, services and data to
its connected devices 104 through its associated servers. Devices 104 connect to network
102 through wired connections to network server 106 which has software and hardware
facilities to manage all communications of data and messages among devices communicating
in network 102. Network 102 can be implemented in any known architecture, providing
wired and / or wireless connections to its elements.
[0028] As part of a typical network architecture elements in system 100 are organized following
a layered model of network functions, such as an OSI model. As is known in the art,
the OSI model defines seven layers where each layer controls functions of specific
network/connection/applications.
[0029] Two OSI layers of particular relevance for an embodiment are the network layer and
the data link layer. Adherence to all necessary connectivity requirements for each
layer is required if device 108 is to remain in communication with all relevant networks
in system 100. Features of both layers are discussed in turn.
[0030] For the data link layer, further detail is provided on an exemplary installation
for network 110 relating to an embodiment. Network 110 is implemented as Wireless
Fidelity (Wi-Fi) networks generally following standards set by the IEEE LAN/MAN Standards
Committee, known as IEEE 802, through its working group "11". The 802.11 standard
defines media access control (MAC) and physical (PHY) layers in the OSI protocol model
for WLAN. Such standards are known to those of skill in the art. Administrative functions
for network 110 may be provided by software controlling it. The software may administer
functions such as network identification and network access parameters. The initial
802.11 standard was followed with a series of amendments, where each amendment was
identified by an alphabetic suffix following in the standard's numeric identifier
"802.11". The family of 802.11 amendments is sometimes referred to as the 802.11x
family. Currently, the 802.11 amendments encompass six wireless modulation techniques
that all use the same communication protocol among their communicating elements. Such
networks are deployed in one or more of the five current versions of 802.11: 802.11
a, b, g and n. These amendments include changes to the IEEE 802.11 PHY. There are
other MAC layer amendments that are known to those of skill in the art. Specific transmission
details and parameters of these networks are known to those of skill in the art.
[0031] For the data link layer, wireless devices 108 communicate with each other through
wireless networks 110. In many environments, networks 110 are local, geographically
small, wireless networks (such as wireless local area networks or WLANs), perhaps
being contained within a single building 112. Wireless devices 108 include handheld
devices, cell phones and computers (either desktop or portable) having a (wireless)
network card, network adapter and/or network interface controller (NIC) installed
therein. There may be one or more networks 110 at a particular site and the geographic
coverage 114 of each network 110 may overlap fully, partially or not at all.
[0032] Network 110 includes an antenna, access point (AP) 116 and supporting radio transmission
equipment known to those skilled in the art. In an embodiment, each AP 116 is an IEEE
802.11 radio receiver/transmitter (or transceiver) and functions as a bridge between
its respective WLAN 110 and network 102. For security, each AP 116 may be communicatively
coupled to network 102 through a respective firewall and/or VPN (not shown). It provides
data distribution services among devices 108 within network 110 and between devices
108 in network 110 and other devices in other connected networks. One distribution
service provided by access point 116 for its related stations is to establish a logical
connection between a device 108 and an access point.
[0033] Interface server 118 in network 102 provides hardware and software systems to allow
network 102 to communicate with wireless networks 110. For communications directed
to wireless devices 108, wireless services enterprise server 120 provides an interface
with server 106 for transmissions destined to devices 108 and vice versa.
[0034] Database 122 provides a data storage system for one or more elements in network 102,
including server 106. Security systems within network 102 can be provided by known
techniques and systems. Gateway 124 provides and monitors selected communications
between elements in network 102 and external devices connected through Internet 126.
[0035] For a 802.11 network, a "station" is a basic component in the network. A station
is any device that implements the functionality of a 802.11 protocol and has a connection
to the wireless network. Typically, the 802.11 connection and communication functions
are implemented in hardware and software and may be provided in a network connection
circuit or system in a NIC at the station. A station may be any device, including
a laptop computer, handheld device 108, or an AP 116. Stations may be mobile, portable,
or stationary. All stations support the 802.11 station services of authentication,
de-authentication, privacy, and data delivery. For the purposes of an embodiment as
it relates to 802.11 standards, devices 108 may be considered to be stations.
[0036] A service set identifier ("SSID") is a unique 32-character network name, or identifier,
that is created and associated with a particular WLAN 110. The SSID can be any alphanumeric
entry up to a maximum of 32 characters and is typically case sensitive. It may be
set by a network administrator using network administration software for a control
server of WLAN 110. The SSID should be chosen so that it differentiates one WLAN from
another. As the SSID differentiates one WLAN from another, any APs and all wireless
and other devices attempting to connect to a specific WLAN may require that a device
provides the correct SSID for that WLAN before permitted the device to join that WLAN.
[0037] Further detail is now provided on messages generated and sent between components
in WLAN 110. In a 802.11-compliant network, messages are sent between its AP 116 and
its communicating devices 108 in data transmissions called frames. Most frames are
sent and processed in a "send-and-respond" protocol. As such a frame may be sent by
an AP 116 to one or more devices 108. When a device receives a frame, it extracts
data from the frame and then it may generate a response. A similar communication dialog
may be initiated by a device 108 to AP 116. Note that broadcast frames sent by an
AP 116 are not acknowledged by stations 108. There are several classes of frames including
control, management and data. Control frames assist in delivering data frames between
stations. Management frames facilitate connection establishment and maintenance between
a device 108 and AP 116. In particular, management frames have the following uses:
they allow a device to be associated, disassociated and re-associated to a network;
they allow a device to be authenticated with a network; and they allow a device to
initiate a probe request to an AP to request information about another device in a
network. Frames may include additional information such as source and destination
MAC addresses, a control field that provides information on the 802.11 protocol version,
frame type and other status indicators. It will be appreciated that a person of skill
in the art has knowledge of the protocols of the frames. Additional materials relating
to same are provided in published 802.11 Working Group materials.
[0038] A beacon frame is a type of a management frame that is periodically broadcast by
an AP 116 to provide a signal of its presence to the communication boundaries of its
network. The typical period of transmission of a beacon frame is about every 100 ms.
802.11 standards set the period to be exactly 102.4 ms. It will be appreciated that
there will be an acceptable variance in the exact period used in an embodiment, which
may be in the range of 10% from the standard period. The body of a beacon frame contains:
a beacon interval, providing the amount of time between beacon transmissions; a timestamp,
which may be used by a station to synchronize itself and update its local clock; and
the SSID of the WLAN 110 of the AP 116. The beacon frame can also provide: data indicating
the supported transmission rates of the WLAN; data regarding the signalling parameters
of the WLAN, such as frequency hopping spread spectrum, direct sequence spread spectrum,
etc.; data on the capabilities of the WLAN; and data providing a traffic indication
map (TIM). The beacon frame includes a frame header and cyclic redundancy checking
(CRC) field. The destination address of the frame is set to all 1's, which is the
broadcast MAC address. This will cause all other stations on the applicable channel
to process a received beacon frame. The beacon frame may also contain a Delivery TIM
(DTIM) which is a flag indicating whether any buffered broadcast or multicast traffic
is going to be transmitted from the AP 116 to device 108 immediately (or shortly)
after the beacon signal.
[0039] Table A below provides a snapshot of some of the typical fields in a beacon frame:
Table A
Field |
Exemplary Value |
Timestamp |
3403424 microseconds |
Beacon Interval |
100 ms |
SSID ID |
0 |
TIM |
|
Element ID |
5 |
TIM element |
Length |
6 |
DTIM Period |
0 |
Bit Offset Map |
1 |
Traffic Indicator |
0 |
The last four parameters are all related to the TIM element.
[0040] A beacon frame is used as a synchronizing signal for transmitting broadcast and multicast
traffic to devices in the associated network. Immediately following the beacon frame,
if broadcast or multicast traffic is queued to be provided, such traffic is transmitted
by AP 116 through its network 112. Mufticast traffic is queued for transmission by
AP 116 only if its requested recipient device 108 has positively responded to an early
request by AP 116 to transmit that multicast traffic to it. Broadcast traffic is broadcast
to the devices 108 without any request signal sent by AP 116. The broadcast or multicast
traffic can contain data from other layers in the communication network, such as the
IP layer. The contents of the Bit Offset Map and the Traffic indicator combined contain
an encoded indication of what type of traffic (i.e. broadcast or multicast) follows
the beacon, if any. Device 108 has an algorithm that can decode the fields to determine
if any such traffic does follow the beacon signal.
[0041] Further detail is now provided on how a device 108 interacts with AP 116 when entering
the coverage area of network 110. Each device 108 that enters a coverage area 114
needs to become associated with the related AP 116 before a communication connection
is made to network 110. Once an association is made, AP 116 is able to use identification
data relating to device 108 to determine where and how to deliver data to that device
108. As a device 108 roams into the coverage area 114, it periodically scans for any
beacon signals on some or all channels on one or more classes of 802.11 network(s).
When a beacon is found, the device extracts data parameters of particular network.
Once the data is extracted, device 108 can analyze the data and adjust parameters
of the power save mode accordingly.
[0042] Additional connection information may then be established for other requirements
of other connection layers in the OSI model. For example, in addition to providing
a data link layer connection between device 108 and AP 116, following the OSI-model,
network 112 is configured to process IP traffic among device 108, AP 116 and other
components in network 102. In order for device 108 to receive IP traffic, it must
maintain an IP connection for device 108 through WLAN 110.
[0043] For the IP connection between device 108 and WLAN 110, in to establish and maintain
an IP connection with WLAN 110, device 108 needs to acquire an Internet Protocol (IP)
address. IP addresses are either static or dynamic. Dynamic IP addressing allows device
108 to move and maintain or re-establish a connection to the Internet and receive
IP traffic. As part of this mobility, WLAN 110 implements a Dynamic Host Configuration
Protocol (DHCP) server to server to dynamically allocate a temporary IP address to
device 108.
[0044] While the MAC address for the device 108 does not change, network 110 needs to be
able to pair a MAC address with the IP address for device 108. Network 110 establishes
this pairing utilizing the Address Resolution Protocol (ARP) (RFC 826), whose parameters
are known in the art. ARP provides for an IP host to establish a mapping between the
MAC and an IP address for device 108. Each device is expected to respond to an ARP
request within a given timeframe. Timely receipt of the response enables the network
to confirm the connection with the device and as such the network can maintain the
connection particulars for the device. As part of the protocol, an AP may learn and
store the IP/MAC address for a specific device 108. In order to adhere to ARP, device
108 must provide a timely response to the ARP request. Any IP unicast frame and Internet
Control Message Protocol (ICMP) request (ping) sent from device 108 to the IP gateway
associated with the WLAN 110 through AP 116 will trigger the IP gateway to update
its ARP table. Any timely ARP response messages that are received by AP 116 are provided
to the IP gateway associated with WLAN 110. The network gateway or router will periodically
update its ARP cache. When the ARP cache entry expires, the device can trigger the
gateway to update its ARP cache by sending it a directed frame. Use of an ICMP request
or ping frame is a logical choice because the gateway will need to do an ARP in order
to reply.
[0045] Network 110 stores newly-learned MAC/IP pairs in a local cache. Similarly, AP 116
may maintain a copy of the cache, which may be periodically flushed and reconciled;
this is known as proxy ARP behaviour. In order for device 108 to maintain its IP connection
with network 110, it is necessary that AP 116 and network 110 have data for a MAC/IP
pair for device 108. As such, device 108 needs to be able to provide a timely response
to any ARP requests generated by AP 116. For example, AP 116 may send a ARP request
message to each device 108 in its ARP cache. When a particular request is sent to
a particular device 108, if that device 108 does not provide a timely ARP response
to AP 116, then the entry for that device in the ARP cache of the AP is subject to
being deleted. Thereafter, the deleted device will not receive any IP traffic that
is addressed to it. Similarly, device 108 maintains an ARP cache of hosts that have
tried to contact it.
[0046] Different periods may be provided for ARP requests for different networks. The periods
may be static or dynamic. The windows for receiving responses may be static or dynamic
as well. Generally, a typical frequency of sending ARP requests is in the range of
minutes, such as once every 4 to 10 minutes.
[0047] In the above noted network, an embodiment provides a power save mode for a device
while maintaining connection requirements of different functional layers of the network's
connection model. One feature of such a power save mode that it selectively turns
off power to one or more modules of its associated device. In device 108, its communication
subsystems consumes a significant amount battery power (see elements 404 and 406 in
Fig. 4). As such, it is useful to minimize activation of those modules during a power
save mode. However, it will be appreciated that during such power save times, no data
traffic can be transmitted or received. As such, those modules are selectively powered
down, but then selectively re-activated for defined periods of time in order to receive
and respond to various network connection requests relating to different functions
in an OSI model. As described earlier, two important functions in a network implementing
an OSI model are the maintenance of the data link connection and the network connection,
namely a 802.11 connection and an IP connection for the network described above. In
order to maximize the power savings, it is preferable to set a power save period that
lasts as long as possible, without losing either connection.
[0048] As noted earlier, as part of the data link layer, AP 116 will periodically send broadcast/multicast
packets towards device 108 at intervals determined, in part, by the value of the DTIM
field (see Table A, earlier). As such, for the power-down mode for device 108, it
must be synchronized such that device 108 is able to receive and respond to such beacon
signals and receive, as required, the broadcast/multicast traffic that precedes them.
[0049] In an embodiment, the power save mode does not have to re-activate device 108 for
each and every data link beacon. The DTIM field contains an integer value indicating
the frequency of the broadcast/multicast downloads relative to the beacon signal.
When there is a station (such as device 108) in power save mode, AP 116 will delay
transmission of broadcast frames until after the beacon with the DTIM. That gives
the sleeping stations an opportunity to receive the beacon. The value of the DTIM
should not be too large because that may cause unacceptable delays in broadcast traffic.
It will also be appreciated that there may be incremental gains in battery life diminishes
as the DTIM increases.
[0050] There is also a tradeoff between battery life savings and WLAN broadcast delays.
As a balance in the trade-off, the DTIM should be set to a value of 2, 3, 4 or around
that range. If it is set to "1" nominally, this indicates that network 110 is set
to be able to provide a broadcast/multicast transfer after each beacon signal. If
the DTIM field is set to 2, 3, 4, etc. then broadcast/multicast traffic is set to
sent after every second, third, fourth etc. beacon signal. Notably, for a Wi-Fi network
carrying IP traffic, even if the DTIM field is 1, there is a high degree of certainty
that there will not be multicast/broadcast IP traffic of interest to the device 108
provided after each beacon signal. Similarly, if the DTIM field is 2, there is also
a good probability that there will not be IP traffic of interest to the device 108
provided after every second beacon signal. Using the above noted discoveries, it is
possible to have a power-down mode for an embodiment, maintain its power save mode
for longer than 1 or 2 beacon intervals and still maintain a data link connection.
It is important to note that there may be a unicast traffic indication within any
specific beacon. However, unlike broadcast traffic, AP 116 buffers the unicast frames
for the station until the station requests that these frames are to be forwarded.
Thus, if device 108 maintains a power save mode for longer than 1 or 2 beacon intervals,
it will still be able to receive unicast traffic.
[0051] As such, in order to maintain a data link connection and to extend the duration of
the power save mode, device 108 can receive and read the DTIM value from the beacon
and then adjust the duration of the power save mode accordingly. In the embodiment,
if the DTIM value in the beacon is 1, then the duration of the power save mode is
set to 3 beacon intervals (i.e. 3 x 102.4 ms = 307.2 ms). For any other value (i.e.
DTIM >= 2), the power save duration is set to that value of the DTIM. In other embodiments,
different timing intervals may be used to respect specific timing requirements for
a particular data link connection. It will be appreciated that if the interval is
too large (for example "9"), then there will be unacceptable delays or losses in the
transmission of broadcast/multicast traffic to all devices connected to the AP.
[0052] As such, when the power save mode re-activates the communication subsystems of device
108, device 108 can then receive the beacon signal, analyse the data in the beacon
signal to determine whether multicast/broadcast traffic is to follow the beacon signal
and then, wait if necessary to receive the data. If no data is to be received, then
the device can return to its power save mode until the next re-activation cycle or
event. If data is to be retrieved, then device 108 may keep the communication subsystems
active for the duration of the transmissions in order to receive and confirm same,
as needed.
[0053] As the DTIM value indicates a de-activation period, the duration of the activation
and deactivation periods need to be monitored. An internal clock in device 108 is
used to track the elapsed time for the power save mode. In order to ensure that the
power save mode should not extend over the estimated time of the next beacon signal.
As such, the power save time can be adjusted slightly downward to allow for the device
to re-activate its communication subsystems to be available to receive the next expected
beacon. For example, if the power save interval is 307.2 ms (or a value near that
amount) because the DTIM value is 1, then the mathematical time between re-activation
for beacon signals is 307.2 ms. However, the actual duration may be 290 ms or some
other value that is offset below 307.2 ms. If there is no broadcast traffic, device
108 will go back to its power save mode after the beacon, which would be in the order
of 5 ms. If there is broadcast traffic, the device will stay awake for 10-20 ms, or
any other time that enables device 108 to receive that traffic. Alternatively or additionally,
it may return to its power save mode upon receiving a signal indicating that transmission
of the traffic has completed. It will be appreciated that in other embodiments, other
multipliers and offsets may be used to set the duration of the power save mode.
[0054] As noted above, the connection between device 108 and network 102 requires both a
data link connection and an IP connection. The above noted re-activation frequency
for the power save mode ensures that the data link connection is maintained. However,
the embodiment adjusts the power save mode to re-activate device 108 to enable it
to respond to specific IP-layer requests related to the IP connection to ensure that
the IP connection is maintained.
[0055] Accordingly, the power save mode needs to be responsive to certain connection requirements
and IP connection messages sent from AP 116 to device 108. As noted above, AP 116
periodically broadcasts ARP signal requests to its network. Device 108 preferably
responds to each ARP request in order to maintain the IP connection for device 108,
even when device 108 is in a power save mode. Notably, responding to ARP request does
not require that device 108 be fully active for the entire period between ARP requests.
As such, the power save mode is designed to activate the communication subsystems
of device 108 in order to enable it to receive and respond to each ARP request that
requires a response. After transmitting an appropriate response, the power save mode
may selectively de-activate the communication subsystems until they are required,
they are activated or the next re-activation cycle for the power save mode is reached.
The next re-activation cycle may be the next predetermined wakeup time arrives for
a subsequent beacon (which may not necessarily be the next beacon). In some configurations,
if the ARP request is set to be sent more frequently than the beacons, then the next
interval that device 108 will be able to receive and respond to ARP requests would
be the next re-activation time.
[0056] In order to establish the period of time between successive ARP requests for the
power save mode, device 108 may need to conduct a discovery process to determine the
ARP timeout period for a host. This may be done by initially monitoring for 2 or more
ARP requests from the host and determine an average time between ARP requests. Using
its internal timer, it can then wake itself up at an appropriate time to receive and
respond to the ARP requests. In some embodiments, device 108 may set the time such
that it simply expects the ARP request to be set at a specific time and then generates
and sends the response. As such, device 108 may generate an ARP when it has determined
that an ARP request is being, just has been, or is about to be sent and then it re-enters
its power save mode. This may be done by device 108 when it makes a new association
with a new wireless network 112.
[0057] It is noted that the discovery process to determine an ARP timeout period for a particular
host may need to be repeated for other hosts in the network, as different hosts may
have different timeout periods. This may not be feasible. As such, the discovery may
be conducted for the default gateway of the network. Alternatively or additionally,
another approach may perform the discovery process on all hosts with which device
108 has communicated with in the network (and that have entries in its own ARP table).
[0058] Other embodiments may implement different timing and synchronization methods. One
approach is as follows. When device 108 is timed to re-activate itself for the ARP,
it may generate and send a unicast frame to the other device from which it is expecting
an ARP request (such as AP 116). This approach does not need to consider any ARP request
and related synchronizations to the request. In this approach, device 108 should preferably
maintain power to its communication systems for a short period after sending the proactive
unicast packet, just in case the other device actually sends an ARP request (which
must be honoured by device 108). Device 108 may also scan its cache and send a unicast
frame to all hosts in the cache.
[0059] It will be appreciated that an embodiment may not require establishment of the time
between successive ARP requests to operate. Alternatively, an embodiment may use a
preset time between ARP requests, such as 120 seconds. Preferably, the preset time
is set such that no host in the network has an ARP timeout below that preset time.
[0060] With the embodiment both the data link and the IP connections are maintained. Gratuitous
ARP responses are also avoided, thereby minimizing the possibilities of having the
network misinterpret the ARP responses as being a "Denial of Service" attack.
[0061] In other embodiments, the parameters may vary on other connection conditions of the
device or in the network, such as battery strength, signal strength, etc.
[0062] Referring to Fig. 2A, flow chart 200 shows a process operating on device 108 used
to determine set timing parameters for the power save period. First at step 202, process
200 starts. At step 204, process 200 receives and extracts DTIM parameters from a
beacon signal. At step 206, an average ARP period is determined from monitoring and
timing successive ARP requests. At step 208, a power save time is determined such
that device 108 is re-activated at each prescribed DTIM power save interval and at
each ARP request interval. The re-activation times are tracked by an internal clock,
representing first and second instances when device 108 awakens from its power save
mode. After each instance of being re-awakened, device 108 may conduct a further action,
depending on the context for re-awakening, in order to maintain an aspect of a connection
to its network. When the system is implemented in a 802.11 network, monitoring of
signals and initiation of commands may follow the functional requirement of 802.11
frames as noted earlier.
[0063] It will be appreciated that other embodiments may have the elements of process 200
in different orders or may have more or less steps and tests therein. Process 200
may be atomized and may be executed by one or more evaluation, monitoring and command
initiation processes operating on device 108. Also, process 200 may operate in the
background on device 108.
[0064] Referring to Fig. 2B, timeline 210 shows an exemplary timeline of activations of
the communication subsystems 404 and 406 according to an embodiment. To begin, it
is presumed that the DTIM value in the beacon signal is set to 1, thereby initiating
an activation frequency of once every 307.2 ms (3 x 102.4 ms) to capture each beacon
third beacon signal. It is also presumed that device 108 has already monitored and
determined the frequency of transmission of the ARP request signals and it has determined
that they are sent once every 2 minutes, but that they are also offset such that they
are sent 50 ms prior to each round minute mark (e.g. 1 minute and 950 ms, 2 minutes
and 950 ms, etc.). Note that at the 102.4 ms and 204.8 ms intervals, beacon signals
would be expected to be received, but the communication subsystems would not be activated
to allow device 108 to process them. Windows 212 illustrate periods of activation
of the communication modules during the power save mode. It can be seen that each
period of activation of device 108, has each window 212 being activated slightly before
the expected receipt of the related beacon or ARP signal. The duration of the window
212 may depend on the requirements for processing relevant communications for a particular
beacon or ARP. The windows 212 may overlap. If such overlapping occurs, then it may
not be necessary to re-activate the device if it has already been re-activated. During
each window 212 device 108 may execute a specific action depending on whether the
window 212 was meant to maintain an aspect of a data link layer connection requirement
or a network layer connection requirement for the network. As an ARP response may
take less time to generate and send, window 212B for processing an ARP request is
shorter that window 212A for processing a beacon. It is noted that an ARP response
generally has to go through the WLAN driver higher into the stack of the AP 116. After
some beacons, there may be broadcast or multicast traffic, so each window 212A may
differ in length from other windows 212A.
[0065] To assist with management of a power mode's re-activation arrangements, a software
application referred to herein as a power save management module may be provided in
device 108. Management of input and display of the power save parameters may be provided
through a graphical user interface (GUI) as part of that module. In the GUI, screen
may be provided implementing selection and activation criteria for one or more power
save modes may be provided using the parameters described herein. Once the parameters
for the power save modes are entered, other processes and systems on device 108 may
monitor for various conditions relating to the status of all various levels of connections
for a network and then compare the connections against the activation conditions set
in the power save management system. If an activation condition is satisfied, the
other processes can recognize this state and then proceed to selectively activate
and de-activate one or more modules for a power save mode.
[0066] Fig. 3 provides general features of an electronic device for processing electronic
communications in accordance with an embodiment of the invention, which is indicated
generally at 108. In the present embodiment, device 108 is based on a computing platform
having functionality of an enhanced personal digital assistant with cellphone and
e-mail features. It is, however, to be understood that device 108 can be based on
construction design and functionality of other electronic devices, such as smart telephones,
desktop computers, pagers or laptops having telephony equipment. In a present embodiment,
electronic device 108 includes a housing 300, an LCD 302, speaker 304, an LED indicator
306, a trackball 308, an ESC ("escape") key 310, keypad 312, a telephone headset comprised
of an ear bud 314 and a microphone 316. Trackball 308 and ESC key 310 can be inwardly
depressed along the path of arrow "A" as a means to provide additional input to device
108.
[0067] It will be understood that housing 300 can be made from any suitable material as
will occur to those of skill in the art and may be suitably formed to house and hold
all components of device 108.
[0068] Device 108 is operable to conduct wireless telephone calls, using any known wireless
phone system such as a Global System for Mobile Communications (GSM) system, Code
Division Multiple Access (CDMA) system, CDMA 2000 system, Cellular Digital Packet
Data (CDPD) system and Time Division Multiple Access (TDMA) system. Other wireless
phone systems can include Wireless WAN (IMS), Wireless MAN (Wi-max or IEEE 802.16),
Wireless LAN (IEEE 802.11), Wireless PAN (IEEE 802.15 and Bluetooth) etc. and any
others that support voice. Additionally, a Bluetooth network may be supported. Other
embodiments include Voice over IP (VoIP) type streaming data communications that can
simulate circuit-switched phone calls. Ear bud 314 can be used to listen to phone
calls and other sound messages and microphone 316 can be used to speak into and input
sound messages to device 108.
[0069] Referring to Fig. 4, functional components of device 108 are provided in schematic
400. The functional components are generally electronic, structural or electromechanical
devices. In particular, microprocessor 402 is provided to control and receive almost
all data, transmissions, inputs and outputs related to device 108. Microprocessor
402 is shown schematically as coupled to keypad 312 and other internal devices. Microprocessor
402 preferably controls the overall operation of the device 108 and its components.
Exemplary microprocessors for microprocessor 402 include microprocessors in the Data
950 (trade-mark) series, the 6200 series and the PXA900 series, all available at one
time from Intel Corporation. Microprocessor 402 is connected to other elements in
device 108 through a series of electrical connections to its various input and output
pins. Microprocessor 402 has an IRQ input line which allows it to receive signals
from various devices. Appropriate interrupt firmware is provided which receives and
reacts to the signals detected on the IRQ line.
[0070] In addition to the microprocessor 402, other internal devices of the device 108 are
shown schematically in Fig. 3. These include: display 302; speaker 304; keypad 312;
communication sub-system 404; short-range communication sub-system 406; auxiliary
I/O devices 408; serial port 410; microphone port 412 for microphone 316; flash memory
414 (which provides persistent storage of data); random access memory (RAM) 416; clock
418 and other device sub-systems (not shown). Device 108 is preferably a two-way radio
frequency (RF) communication device having voice and data communication capabilities.
In addition, device 108 preferably has the capability to communicate with other computer
systems via the Internet.
[0071] Operating system software executed by the microprocessor 402 is preferably stored
in a computer-readable medium, such as flash memory 414, but may be stored in other
types of memory devices, such as read-only memory (ROM) or similar storage element.
In addition, system software, specific device applications, or parts thereof, may
be temporarily loaded into a volatile store, such as RAM 416. Communication signals
received by the mobile device may also be stored to RAM 416.
[0072] In addition to an operating system operating on device 108, additional software modules
420 enable execution of software applications on device 108. A set of software (or
firmware) applications, generally identified as applications 420, that control basic
device operations, such as voice communication module 420 and data communication module
420B, may be installed on the device 108 during manufacture or downloaded thereafter.
As well, other software modules are provided, such as calendar module 420C, address
book 420D and location module 420E.
[0073] Power save management module 420M is software and / or firmware that provides processes
to receive and update trigger conditions for a power save mode implemented by an embodiment.
A series of GUIs are provided allowing the user to select, for example, the frequency
at which beacon signals are monitored, the duration of any monitoring window and how
the average for the ARP request period is set.
[0074] Network connection module (NCM) 420N is software and / or firmware that provides
processes to detect and analyze when device 108 is in communication contact with one
or more networks 110 and determine the parameters of each communicating network 110
both at the data link layer and the IP connection layer. It may also control when
to seek a connection to a particular network and when to enter, activate, deactivate
the power save mode described earlier. When NCM 420N is used to monitor 802.11x networks
and issue commands relating thereto, the monitoring of signals and the initiation
of commands may follow the functional requirement of 802.11 frames as noted earlier.
NCM 420N also has the ability to selectively activate and deactivate parts of the
components providing communication functions described below. In some embodiments,
NCM 420N provides support for the IP stack and the communication (radio) drivers as
well as their management. In other embodiments, NCM 420N provides support for the
IP stack and the related radio drivers alone.
[0075] Additional modules such as personal information manager (PIM) application may be
provided. Any module may be installed during manufacture or downloaded thereafter
into device 108.
[0076] Data associated with each application, the status of one or more networks, profiles
for networks and trigger conditions for commands for networks can be stored and updated
in flash memory 414.
[0077] Communication functions, including data and voice communications, are performed through
the communication sub-system 404 and the short-range communication sub-system 406.
Collectively, sub-systems 404 and 406 provide the signal-level interface for all communication
technologies processed by device 108. Various applications 420 provide the operational
controls to further process and log the communications. Communication sub-system 404
includes receiver 422, transmitter 424 and one or more antennas, illustrated as receive
antenna 426 and transmit antenna 428. In addition, communication sub-system 404 also
includes processing modules, such as digital signal processor (DSP) 430 and local
oscillators (LOs) 432. The specific design and implementation of communication sub-system
404 is dependent upon the communication network in which device 108 is intended to
operate. For example, communication sub-system 404 of device 108 may operate with
the Mobitex (trade-mark), DataTAC (trade-mark) or General Packet Radio Service (GPRS)
mobile data communication networks and also operate with any of a variety of voice
communication networks, such as 802.11 networks, Bluetooth networks, Advanced Mobile
Phone Service (AMPS), Time Division Multiple Access (TDMA), Code Division Multiple
Access (CDMA), CDMA 2000, Personal Communication Service (PCS), Global System for
Mobile Communication (GSM), WWAN (cellular), WMAN (Wi-max), WLAN (WiFi), and WPAN
(Bluetooth) in other disclosures, etc. Other types of data and voice (telephonic)
networks, both separate and integrated, may also be utilized with device 108. In any
event, communication sub-system 404 provides device 108 with the capability of communicating
with other devices using various communication technologies, including instant messaging
(IM) systems, text messaging (TM) systems and short message service (SMS) systems.
[0078] Short-range communication sub-system 406 enables communication between device 108
and other proximate systems or devices, which need not necessarily be similar devices.
For example, the short-range communication sub-system may include an infrared device
and associated circuits and components, a Wi-Fi or a Bluetooth (trade-mark) communication
module to provide for communication with similarly enabled systems and devices. Sub-system
406 may have one or more inputs or outputs to sub-system 404 in processing signals
for its networks.
[0079] In addition to processing communication signals, DSP 430 provides control of receiver
426 and transmitter 424. For example, gains applied to communication signals in receiver
426 and transmitter 424 may be adaptively controlled through automatic gain-control
algorithms implemented in DSP 430. One particular operational aspect of receiver 422
and antenna 426 is that they need to be tuned to receive signals in the 802.11 network
bands, e.g. signals in the 2.4 GHz to 5.8 GHz range for sub-systems 406 and if needed,
sub-system 404. Additional filters on antenna may also be used to provide such functionality.
[0080] Receiver 422, antenna 426 and network connection module (NCM) 420N provide at least
some of the hardware and software elements needed to detect when device 108 is in
the presence of communication signals from network 110, thereby enabling device 108
to communication with other devices in network 110.
[0081] NCM 420N can receive and interpret the signals and can generate its own signals for
transmission to network 110. The strengths of received signals may also be determined
by NCM 420N. As described earlier, NCM 420N also has system and processes that controls
the activation of the subsystems 404 and 406.
[0082] For example, if a first connection condition relating to the data link layer was
to respond to every third beacon and second condition relating to the network layer
was to respond to each ARP request, then NCM 420N may operate as follows to implement
a power save mode.
[0083] First, NCM 420N sets controls for communication sub-systems 406 or 404 of device
108 to sleep after the receipt of a beacon signal and then enter a power save mode
for the next beacon signal, but re-awake for the third signal. When subsystems 404
and 406 are re-activated, device 108 can receive the (third) beacon signal and analyse
its contents. If the beacon signal indicates that broadcast/multicast traffic is slated
to follow it (via the encoded contents of the Bit Offset Map and the Traffic Indicator
fields), then the device maintains the activation of subsystems 404 and 406 in order
to receive that traffic, per the normal full power operation of device 108. Once the
traffic is fully received and all relevant acknowledgement or error signals have been
transmitted by device 108, the power save mode can then deactivate subsystems 404
and 406. As the power save mode has knowledge of the number of DTIM periods to sleep,
an internal clock and counter can be used to determine the period of inactivation
that would enable the power save mode to deactivate subsystems 404 and 406 immediately
following a certain beacon signal and then re-activate those subsystems shortly before
the anticipated receipt of the third beacon signal (or any other period that is used)
and the timer may be reset (or not). The mechanism for tracking the clock and counter
and issuing a re-activation signal may be implemented through an interrupt routine
on device 108.
[0084] Second, in addition in order to maintain the connection for the network layer, device
108 needs to be able to receive and respond to each ARP request sent by an AP 116
while device 108 is within network 112. The period of transmissions of successive
ARP requests has been noted to be in the order of minutes. For any power save mode,
the last instance of the ARP request needs to be tracked and a timer initialized to
track when the next expected ARP request is to be expected to be received. Again,
this timer may be implemented through an interrupt routine on device 108. Once the
timer provides its signal, the power save mode should re-activate subsystems 404 and
406. Then device 108 needs to wait for the expected next ARP request and then generate
and transmit an appropriate response ping. Thereafter the power save mode may again
de-activate subsystems 404 and 406 and the timer may be reset (or not). Alternatively
or additionally, device 108 may anticipate an ARP request and generate and ARP response,
or it may anticipate the ARP timeout and generate a unicast frame to the gateway such
as an ICMP request (a ping). Device 108 may also review its ARP cache and send additional
unicast frames to other hosts in its table thereby ensuring that all hosts known by
device 108 are contacted.
[0085] The next instance of the re-activation of subsystems 404 and 406 would be the earlier
of the next activation cycle based on the beacon signals or the next activation cycle
based on the ARP requests. In some cycles, the two activation cycles may overlap in
whole or in part.
[0086] The power save mode may be activated upon predetermined conditions for device 108
or network 112. Exemplary conditions include entering the power save mode: after a
predetermined time of non-use of device 108, after a predetermined period of no traffic
sent between device 108 and network 112 or in either direction from or to device 108;
or dependent on what application is running on the device; at a predetermined time
(e.g. after 12:00 am); when device is at a predetermined location, etc. It is noted
that IEEE 802.11 refers to the WLAN power save mode as "802.11 Power Save (PS)", for
which features thereof may be incorporated into an embodiment.
[0087] Powering the entire electronics of the mobile handheld communication device is power
source 434. In one embodiment, the power source 434 includes one or more batteries.
In another embodiment, the power source 434 is a single battery pack, especially a
rechargeable battery pack. A power switch (not shown) provides an "on/off switch for
device 108. A power source interface (not shown) may be provided in hardware, firmware,
software or a combination of such elements to selectively control access of components
in device 108 to power source 434. Upon activation of the power switch an application
420 is initiated to turn on device 108. Upon deactivation of the power switch, an
application 420 is initiated to turn off device 108. Power to device 108 may also
be controlled by other devices and by software applications 420.
[0088] Device 108 may also have global positioning system 436 to assist in identifying a
present location of device 108 and may also have light sensor 438 to provide data
on the ambient light conditions for device 108.
[0089] Although an embodiment has been described in terms of maintaining a data link connection
for a 802.11 network and a connection link to an IP network, the features of an embodiment
can be provided in other network technologies and other requirements for other layers
in the OSI model. A notable feature of an embodiment is that more than one connection
requirement is monitored and addressed while a device is in a power save mode.
[0090] In other embodiments, the power save mode may cause the subsystems 404 and 406 to
re-activate themselves based on receipt of a signal indicating some event. As the
subsystems 404 and 406 may not be powered, the signal may not originate externally.
Alternatively or additionally, if subsystems 404 and 406 are placed in a low power
operating mode, they may still be able to receive and transmit signals, albeit at
perhaps a lower power level. In such an environment, the power save mode may monitor
for specific "wake up" signals to trigger the (full or further) re-activation of subsystems
404 and 406.
[0091] In other embodiments, the two connection conditions may be in the same "layer" of
the connection model governing the network.
[0092] It will be appreciated that PSM 402M, NCM 420N and other applications in the embodiments
can be implemented using known programming techniques, languages and algorithms. The
titles of the modules are provided as a convenience to provide labels and assign functions
to certain modules. It is not required that each module perform only its functions
as described above. As such, specific functionalities for each application may be
moved between applications or separated into different applications. Modules may be
contained within other modules. Different signalling techniques may be used to communicate
information between applications using known programming techniques. Known data storage,
access and update algorithms allow data to be shared between applications. For example,
detection or completion of an event described in Fig. 2A may cause an interrupt to
be generated on microprocessor 402 and a particular interrupt routine may be provided
to process the event. It will further be appreciated that other applications and systems
on device 108 may be executing concurrently with PSM 402M, NCM 420N or other modules.
As such, PSM 420M and NCM 420N may be structured to operate in as a "background" application
on device 108, using programming techniques known in the art.
[0093] Further in other embodiments, power save modes may be designed to work with Wi-Max
networks, i.e. 802.16-class networks, in place of 802.11-class networks.
[0094] The present invention is defined by the claims appended hereto, with the foregoing
description being merely illustrative of embodiments of the invention. Those of ordinary
skill may envisage certain modifications to the foregoing embodiments which, although
not explicitly discussed herein, do not depart from the scope of the invention, as
defined by the appended claims.
1. A method for conserving power for a communication device (108) having a network layer
connection to a network (102) through a transceiver (116), comprising:
in a first cycle, at a first instance in a first period of time (212A) monitoring
for a Medium Access Control 'MAC' beacon signal relating to a data link layer connection
from the transceiver (116) during the first period (212A), the first period timed
to allow the device to receive the MAC beacon signal and the first cycle having a
frequency based on a frequency of occurrence of the MAC beacon signal; and
in a second cycle, for a second period (212B) beginning at a second instance in the
second cycle, monitoring for an Address Resolution Protocol 'ARP' request for an Internet
Protocol 'IP' address relating to the network layer communication from the transceiver
(116) during the second period, the second cycle having a frequency which is shorter
than the frequency of transmission of the ARP from a host in the network.
2. The method as claimed in claim 1, wherein the method further comprises:
in the first cycle, at the first instance re-activating a communication subsystem
(404) in the device (108) and de-activating the communication subsystem (404) after
the end of the first period.
3. The method as claimed in claim 2, wherein the method further comprises:
in the second cycle at the second instance re-activating the communication subsystem
(404) and de-activating the communication subsystem (404) after the end of the second
period.
4. The method as claimed in any one of claims 1 to 3, wherein the network (102) is a
802.11-class network.
5. The method as claimed in any one of claims 2 or claims 3 to 4 when depending on claim
2, wherein for the first period (212A):
if the MAC beacon signal indicates broadcast or multicast traffic from the network
(102) intended for the device (108) follows the MAC beacon signal, the communication
subsystem (404) is de-activated after an end of transmission of the broadcast or multicast
traffic; and
if the MAC beacon signal indicates that no broadcast or multicast traffic from the
network (102) intended for the device (108) follows the beacon signal, the communication
subsystem (404) is de-activated after completion of reception of the MAC beacon signal.
6. The method as claimed in any one of claims 1 to 5, wherein during the second period
a unicast frame is transmitted to a host in the network (102) by the device (108).
7. The method as claimed in any one of claims 1 to 6, wherein the first cycle is determined
from a delivery traffic indication map 'DTIM' value in the MAC beacon, such that if
the DTIM value equals 1, then the first cycle is set to be related to a larger DTIM
value.
8. The method as claimed in claim 7, wherein the DTIM value is used to indicate a de-activation
period for the at least one communication subsystem (404).
9. The method as claimed in any one of claims 1 to 8, wherein a clock in the device (108)
tracks an elapsed time between receipt of the ARP request and receipt of a next ARP
request to determine the second period of the power save mode.
10. The method as claimed in claim 7, wherein if the DTIM value equals 1, then the first
cycle is set to span three MAC beacon signal intervals.
11. The method as claimed in claim 7, wherein the first cycle is set to span between a
number of MAC beacon signal intervals larger than the DTIM value and eight MAC beacon
signal intervals.
12. The method as claimed in any one of claims 1 to 11, wherein the first period (212A)
is extended for a predetermined period when broadcast traffic to the device (108)
from the network (102) is being sent to the device (108) to allow the device (108)
to receive the broadcast traffic.
13. The method as claimed in any one of claim 2 or claims 3 to 12 when depending on claim
2, wherein the first period (212A) is reduced by a first offset relating to a time
required by the device to re-activate the communication subsystem (404).
14. A communication device (108) having a power save mode, comprising:
at least one communication subsystem (404) providing transmission and reception of
signals with a communication network (102);
a microprocessor (402);
a timer (418);
a first module to selectively activate and de-activate the communication subsystem
(404) when the device (108) is operating in the power save mode; and
a second module to control the first module and the communication subsystem (404)
while the device (108) is in the power save mode such that the communication device
(108) is caused to perform the steps of the method of any one of claim 2 or claims
3-13 when depending on claim 2.
15. A computer readable medium storing computer readable instructions executable by a
processor (402) of a computing device (108) to cause the device (108) to implement
the steps of the method of any one of claims 1 to 13.
1. Verfahren zum Sparen von Energie für eine Kommunikationsvorrichtung (108), die eine
Netzschichtverbindung an ein Netz (102) durch einen Sende-Empfänger (116) hat, mit:
Überwachen in einem ersten Zyklus zu einem ersten Zeitpunkt in einer ersten Zeitdauer
(212A) nach einem Medium-Access-Control-, "MAC"-, Bakesignal, das sich auf eine Datenlinkschichtverbindung
von dem Sende-Empfänger (116) bezieht, während der ersten Dauer (212A), wobei die
erste Dauer zeitlich derart abgepasst ist, um der Vorrichtung zu ermöglichen, das
MAC-Bakesignal zu empfangen, und wobei der erste Zyklus eine Frequenz auf Grundlage
einer Auftretensfrequenz des MAC-Bakesignals hat, und
Überwachen in einem zweiten Zyklus während einer zweiten Dauer (212B), die zu einem
zweiten Zeitpunkt in dem zweiten Zyklus anfängt, nach einer Adressauflösungsprotokoll-,
"Address-Resolution-Protocol"-, 'ARP'-, Anfrage nach einer Internetprotokoll-, 'IP'-,
Adresse, die sich auf die Netzschichtkommunikation bezieht, von dem Sende-Empfänger
(116) während der zweiten Dauer, wobei der zweite Zyklus eine Frequenz hat, die kürzer
als die Sendefrequenz des ARP von einem Host in dem Netz ist.
2. Verfahren nach Anspruch 1, wobei das Verfahren ferner Folgendes aufweist:
Reaktivieren eines Kommunikationsteilsystems (404) in der Vorrichtung (108) in dem
ersten Zyklus zu dem ersten Zeitpunkt und Deaktivieren des Kommunikationsteilsystems
(404) nach dem Ende der ersten Dauer.
3. Verfahren nach Anspruch 2, wobei das Verfahren ferner Folgendes aufweist:
Reaktivieren des Kommunikationsteilsystems (404) in dem zweiten Zyklus zu dem zweiten
Zeitpunkt und Deaktivieren des Kommunikationsteilsystems (404) nach dem Ende der zweiten
Dauer.
4. Verfahren nach einem der Ansprüche 1 bis 3, wobei das Netz (102) ein 802.11-Klasse-Netz
ist.
5. Verfahren nach einem der Ansprüche 2 oder 3 bis 4, wenn von Anspruch 2 abhängig, wobei
während der ersten Dauer (212A):
wenn das MAC-Bakesignal anzeigt, dass Broadcast- oder Multicastverkehr von dem Netz
(102), der für die Vorrichtung (108) vorgesehen ist, dem MAC-Bakesignal folgt, das
Kommunikationsteilsystem (404) nach einem Übermittlungsende des Broadcast- oder Multicastverkehrs
deaktiviert wird, und
wenn das MAC-Bakesignal anzeigt, dass kein Broadcast- oder Multicastverkehr von dem
Netz (102), der für die Vorrichtung (108) vorgesehen ist, dem Bakesignal folgt, das
Kommunikationsteilsystem (404) nach Vollendung eines Empfangs des MAC-Bakesignals
deaktiviert wird.
6. Verfahren nach einem der Ansprüche 1 bis 5, wobei während der zweiten Dauer von der
Vorrichtung (108) ein Unicastrahmen an einen Host im Netz (102) übermittelt wird.
7. Verfahren nach einem der Ansprüche 1 bis 6, wobei der erste Zyklus aus einem Lieferverkehrsangabekarten-,
"Delivery-Traffic-Indication-Map"-, 'DTIM'-, Wert in der MAC-Bake bestimmt wird, so
dass, wenn der DTIM-Wert gleich 1 ist, dann der erste Zyklus eingestellt wird, um
sich auf einen höheren DTIM-Wert zu beziehen.
8. Verfahren nach Anspruch 7, wobei der DTIM-Wert verwendet wird, um eine Deaktivierungsdauer
für das mindestens eine Kommunikationsteilsystem (404) anzuzeigen.
9. Verfahren nach einem der Ansprüche 1 bis 8, wobei eine Uhr in der Vorrichtung (108)
eine abgelaufene Zeit zwischen Empfang der ARP-Anfrage und Empfang einer folgenden
ARP-Anfrage erfasst, um die zweite Zeitdauer des Energiesparmodus zu bestimmen.
10. Verfahren nach Anspruch 7, wobei, wenn der DTIM-Wert gleich 1 ist, dann der erste
Zyklus eingestellt wird, dass er sich über drei MAC-Bakesignal-Intervalle erstreckt.
11. Verfahren nach Anspruch 7, wobei der erste Zyklus eingestellt wird, dass er sich zwischen
einer Anzahl von MAC-Bakesignal-Intervallen größer als der DTIM-Wert und acht MAC-Bakesignal-Intervallen
erstreckt.
12. Verfahren nach Anspruch 1 bis 11, wobei die erste Dauer (212A) für eine vorbestimmte
Dauer verlängert wird, wenn der Broadcastverkehr zu der Vorrichtung (108) von dem
Netz (102) gerade an die Vorrichtung (108) gesendet wird, um der Vorrichtung (108)
zu ermöglichen, den Broadcastverkehr zu empfangen.
13. Verfahren nach Anspruch 2 oder einem der Ansprüche 3 bis 12, wenn von Anspruch 2 abhängig,
wobei die erste Dauer (212A) um einen ersten Versatz reduziert wird, der sich auf
eine Zeit bezieht, die von der Vorrichtung benötigt wird, um das Kommunikationsteilsystem
(404) zu reaktivieren.
14. Kommunikationsvorrichtung (108), der einen Energiesparmodus hat, mit:
mindestens einem Kommunikationsteilsystem (404), das Übermittlung und Empfang von
Signalen mit einem Kommunikationsnetz (102) bereitstellt,
einem Mikroprozessor (402),
einem Zeitgeber (418),
einem ersten Modul, um das Kommunikationsteilsystem (404) selektiv zu aktivieren und
zu deaktivieren, wenn die Vorrichtung (108) in dem Energiesparmodus arbeitet, und
einem zweiten Modul, um das erste Modul und das Kommunikationsteilsystem (404), während
die Vorrichtung (108) in dem Energiesparmodus ist, derart zu steuern, dass die Kommunikationsvorrichtung
(108) veranlasst wird, die Schritte des Verfahrens nach einem der Ansprüche 2 oder
3 bis 13, wenn von Anspruch 2 abhängig, durchzuführen.
15. Computerlesbares Medium, der computerlesbare Anweisungen speichert, die von einem
Prozessor (402) einer Computervorrichtung (108) ausführbar sind, um die Vorrichtung
(108) zu veranlassen, die Schritte des Verfahrens nach einem der Ansprüche 1 bis 13
umzusetzen.
1. Procédé pour économiser de l'énergie pour un dispositif de communication (108) ayant
une connexion de couche réseau à un réseau (102) par l'intermédiaire d'un émetteur-récepteur
(116), comprenant :
dans un premier cycle, à une première instance dans une première période de temps
(212A) la surveillance pour un signal de balise de Contrôle d'accès au support `MAC'
relatif à une connexion de couche liaison de données à partir de l'émetteur-récepteur
(116) pendant la première période (212A), la première période temporisée pour permettre
au dispositif de recevoir le signal de balise MAC et le premier cycle ayant une fréquence
basée sur une fréquence d'occurrence du signal de balise MAC ; et
dans un second cycle, pour une seconde période (212B) commençant à une seconde instance
dans le second cycle, la surveillance pour une demande de Protocole de résolution
d'adresse 'ARP' pour une adresse de Protocole Internet 'IP' relative à la communication
de couche réseau à partir de l'émetteur-récepteur (116) pendant la seconde période,
le second cycle ayant une fréquence qui est plus courte que la fréquence de transmission
de l'ARP à partir d'un hôte dans le réseau.
2. Procédé selon la revendication 1, dans lequel le procédé comprend en outre :
dans le premier cycle, à la première instance la réactivation d'un sous-système de
communication (404) dans le dispositif (108) et la désactivation du sous-système de
communication (404) après la fin de la première période.
3. Procédé selon la revendication 2, dans lequel le procédé comprend en outre :
dans le second cycle à la seconde instance la réactivation du sous-système de communication
(404) et la désactivation du sous-système de communication (404) après la fin de la
seconde période.
4. Procédé selon l'une quelconque des revendications 1 à 3, dans lequel le réseau (102)
est un réseau de classe 802.11.
5. Procédé selon l'une quelconque de la revendication 2 ou des revendications 3 à 4 lorsqu'elles
dépendent de la revendication 2, dans lequel pour la première période (212A) :
si le signal de balise MAC indique qu'un trafic de diffusion ou de multidiffusion
à partir du réseau (102) destiné au dispositif (108) suit le signal de balise MAC,
le sous-système de communication (404) est désactivé après une fin de transmission
du trafic de diffusion ou de multidiffusion ; et
si le signal de balise MAC indique qu'aucun trafic de diffusion ou de multidiffusion
à partir du réseau (102) destiné au dispositif (108) ne suit le signal de balise,
le sous-système de communication (404) est désactivé après l'achèvement de réception
du signal de balise MAC.
6. Procédé selon l'une quelconque des revendications 1 à 5, dans lequel pendant la seconde
période une trame d'unidiffusion est transmise à un hôte dans le réseau (102) par
le dispositif (108).
7. Procédé selon l'une quelconque des revendications 1 à 6, dans lequel le premier cycle
est déterminé à partir d'une valeur de carte d'indication de trafic de remise 'DTIM'
dans la balise MAC, de sorte que si la valeur DTIM est égale à 1, alors le premier
cycle est réglé pour être lié à une valeur DTIM plus grande.
8. Procédé selon la revendication 7, dans lequel la valeur DTIM est utilisée pour indiquer
une période de désactivation pour le au moins un sous-système de communication (404).
9. Procédé selon l'une quelconque des revendications 1 à 8, dans lequel une horloge dans
le dispositif (108) suit un temps écoulé entre la réception de la demande ARP et la
réception d'une demande ARP suivante pour déterminer la seconde période du mode d'économie
d'énergie.
10. Procédé selon la revendication 7, dans lequel si la valeur DTIM est égale à 1, alors
le premier cycle est réglé pour couvrir trois intervalles de signal de balise MAC.
11. Procédé selon la revendication 7, dans lequel le premier cycle est réglé pour couvrir
entre un nombre d'intervalles de signal de balise MAC plus grand que la valeur DTIM
et huit intervalles de signal de balise MAC.
12. Procédé selon l'une quelconque des revendications 1 à 11, dans lequel la première
période (212A) est prolongée pour une période prédéterminée lorsqu'un trafic de diffusion
vers le dispositif (108) à partir du réseau (102) est envoyé au dispositif (108) pour
permettre au dispositif (108) de recevoir le trafic de diffusion.
13. Procédé selon l'une quelconque de la revendication 2 ou des revendications 3 à 12
lorsqu'elles dépendent de la revendication 2, dans lequel la première période (212A)
est réduite d'un premier décalage relatif à un temps requis par le dispositif pour
réactiver le sous-système de communication (404).
14. Dispositif de communication (108) ayant un mode d'économie d'énergie, comprenant :
au moins un sous-système de communication (404) fournissant la transmission et la
réception de signaux avec un réseau de communication (102) ;
un microprocesseur (402) ;
un temporisateur (418) ;
un premier module pour activer et désactiver sélectivement le sous-système de communication
(404) lorsque le dispositif (108) fonctionne dans le mode d'économie d'énergie ; et
un second module pour commander le premier module et le sous-système de communication
(404) pendant que le dispositif (108) est dans le mode d'économie d'énergie de sorte
que le dispositif de communication (108) soit amené à effectuer les étapes du procédé
selon l'une quelconque de la revendication 2 ou des revendications 3 à 13 lorsqu'elles
dépendent de la revendication 2.
15. Support lisible par ordinateur stockant des instructions lisibles par ordinateur exécutables
par un processeur (402) d'un dispositif informatique (108) pour amener le dispositif
(108) à mettre en oeuvre les étapes du procédé selon l'une quelconque des revendications
1 à 13.